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The polar vortex is a large area of low pressure and cold air surrounding both of the Earth’s poles. It ALWAYS exists near the poles, but weakens in summer and strengthens in winter. The term “vortex” refers to the counter-clockwise flow of air that helps keep the colder air near the Poles.

Many times during winter in the northern hemisphere, the polar vortex will expand, sending cold air southward with the jet stream (see graphic above). This occurs fairly regularly during wintertime and is often associated with large outbreaks of Arctic air in the United States. The one that occurred January 2014 is similar to many other cold outbreaks that have occurred in the past, including several notable colder outbreaks in 1977, 1982, 1985 and 1989.
https://www.weather.gov/safety/cold-polar-vortex

Climate, Ice & Weather Whiplash“:
7 minute video: http://youtu.be/u7EHvfaY8Zs

Since the Arctic is warming faster than mid-latitudes, there is a decrease in temperature gradient between the two. The temperature gradient drives the polar jet stream’s westerly wind speed. Thus, decrease in temperature gradient means lower wind speeds, and a slower polar jet stream which is more meandering, and travels more slowly, leading to more extreme weather events. See details on video and in article below.

Excerpted from Francis & Skific, 2015: “A variety of positive feedbacks—processes that amplify an original change—cause the Arctic to be more sensitive to global temperature change than anywhere else on the Earth (e.g. [1,2]). This heightened sensitivity is known as Arctic amplification (AA). Consequently, the Arctic’s lower tropospheric air temperature has continued to rise at least twice as fast as in the Northern Hemisphere’s mid-latitudes during recent decadesSeveral mechanisms have been proposed that explain how AA may influence the large-scale circulation of the Northern Hemisphere and, in particular, the polar jet stream. One hypothesis connects AA to more persistent mid-latitude weather patterns through its effects on the configuration of the jet stream. AA has reduced the Arctic/mid-latitude temperature contrast in recent decades, particularly during autumn and winter ([9]; FV15). Because this temperature gradient is a fundamental driver of the jet stream’s westerly (zonal) wind speed, the weaker gradient leads to slower zonal jet-stream winds [10–12]. A slower jet stream tends to take a more meandering (meridional) path as it encircles the Northern Hemisphere [13,14]. Large north–south jet-stream waves in a highly meandering flow tend to travel eastward more slowly. These waves create the high- and low-pressure systems at the surface, so their slower eastward progression increases the likelihood of persistent weather patterns that can cause a variety of extreme events [15]. Several recent studies have identified a mechanism linking ice loss in the Barents/Kara Seas (BK) area of the Arctic Ocean during autumn with anomalously cold winters in central Asia [16–18]… This new manifestation of global warming through AA may have substantial societal impact, as more frequent extreme weather events in mid-latitudes will affect billions of people directly through damage to property and infrastructure, and indirectly through agriculture and water supplies. Moreover, the amplified patterns exhibit regional preferences for anomalies in temperature and precipitation (e.g. [15,17]), thus it may be possible to predict which types of extreme events will be more likely to occur in certain areas and, in turn, assist decision-makers in preparing for the future. However, because the atmosphere is inherently chaotic and the signal of AA has emerged only recently, it is a challenge to detect robust changes in the character of the jet stream [22,23] and separate the various influences on its behaviour“. ( Francis J, Skific N. 2015, “Evidence linking rapid Arctic warming to mid-latitude weather patterns“. Phil. Trans. R. Soc. A 373: 20140170.











CC-BY: Francis J, Skific N. 2015 “Evidence linking rapid Arctic warming to mid-latitude weather patterns:. Phil. Trans. R. Soc. A 373: 20140170 (Emphasis our own). Original here: https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.2014.0170
http://creativecommons.org/licenses/by/4.0/

Related: https://en.wikipedia.org/wiki/Ice–albedo_feedback

Already in 2014, Trump was blabbering:
Fox Regular Donald Trump Decries Climate Change “Hoax”
Attributes Climate Warnings To Scientists “Having A Lot Of Fun

Video January 6, 2014 9:49 AM EST MEDIA MATTERS STAFF https://www.mediamatters.org/video/2014/01/06/fox-regular-donald-trump-decries-climate-change/197432